It depends what kind they are. Cories do that naturally as a means of getting air. You didn't answer the questions above. Seen as though you have fish in mind, I suggest you research them to find out what they need and go from there. You really need to think about this when you want plecs because they will take up a lot of bio-load in such a small water volume. Maybe try Aquarist Classified and eBay or maybe Ad Trader. I have used them to get stuff in the past.